Exactly, after 50 years it could be anything. Checking the flywheel or damper is pointless unless the guy knows 100% that it is a factory original engine that is untouched. It is very common for people to bolt together a pile of parts and sell it as "numbers matching". I've seen some auction cars that were sold as numbers cars but the engine is a collection of random stuff. 440 six pack top end on a motor home bottom end and stuff like that.